EP4291869A1

EP4291869A1 - Method for monitoring a gearbox in an aircraft, monitoring system for a gearbox in an aircraft, and aircraft having the monitoring system

Info

Publication number: EP4291869A1
Application number: EP22713536.5A
Authority: EP
Inventors: Sergej Lieder; Timm Rösener; Jörg LITZBA
Original assignee: Airbus Helicopters Technik GmbH
Current assignee: Airbus Helicopters Technik GmbH
Priority date: 2021-02-11
Filing date: 2022-02-10
Publication date: 2023-12-20
Also published as: JP2024506197A; WO2022171710A1; US20240117872A1; JP7535196B2; KR20230140582A; DE102021201290A1

Abstract

A method is described for monitoring a gearbox (2) in an aircraft (1), the gearbox (2) having at least one gearbox section (2) with at least one measurement area (M), and a first and a second electrical contact (13, 16) being arranged in the measurement area (M1) at a distance (A) from one another, in which method: a magnetic field (F) is generated in the gearbox section (2), the magnetic field (F) being designed to move at least one ferromagnetic particle (17) arranged in the gearbox section (2) toward the measurement area (M1) such that a bridge (16) is formed from one or more of the ferromagnetic particles (17) between the two electrical contacts (13, 14); on the basis of an electrical characteristic value between the two electrical contacts (13, 16), a measurement value is produced; on the basis of the measurement value, a degree of criticality for flight operation is determined.

Description

Method for monitoring a gearbox in an aircraft.

Monitoring system for a gearbox in an aircraft and aircraft with the monitoring system

The invention relates to a method for monitoring a gearbox in an aircraft with the features of the preamble of claim 1. The invention also relates to a monitoring system for a gearbox in an aircraft and an aircraft with the monitoring system.

In the case of gearboxes in aircraft or helicopters, high torques can occur, which can cause wear or natural abrasion on the gearbox components. It is therefore necessary to monitor the condition of the gearbox to ensure smooth and safe flight operations. For this purpose, sensors for detecting ferromagnetic particles are known, in which a magnetic field is generated in order to attract the ferromagnetic particles and to detect them using a suitable detector.

For example, the publication DE 102012219242 A1 discloses a measuring device for detecting ferromagnetic particles that are movably arranged in a liquid volume, the measuring device having a magnet for generating a magnetic field in the liquid volume, a measuring device for the total electrical resistance of the liquid volume with the liquid therein befindli Chen ferromagnetic particles and means for functional testing of the measuring device with at least one low-impedance resistor between 50 and 500 ohms for performing a resistance measurement.

The object of the invention is to propose a method for monitoring a transmission which provides qualitative information about the condition of the transmission. Furthermore, it is an object of the invention to propose a corresponding monitoring system and an aircraft with the monitoring system. This object is achieved by a method having the features of claim 1, a monitoring system having the features of claim 9 and an aircraft having the features of claim 14. Preferred or advantageous embodiments of the invention result from the dependent claims, the following description and the attached figures.

Within the scope of the invention, a method for monitoring a transmission in an aircraft is proposed. The transmission has a transmission section with at least or exactly one measuring range. The transmission section can be defined by a transmission interior of the transmission or a partial space of the transmission interior. The measuring area is preferably arranged in an area of an oil sump and/or a bottom area of the transmission. Alternatively, however, the at least one measuring area can also be arranged at any other point of the transmission section in which increased wear or abrasion of the transmission components is to be expected. Ultimately, it is provided that the measuring area is in any case arranged in an area in which an oil flow takes place. For example, a volume of oil can be injected into a bearing through an oil nozzle, so that the oil absorbs particles as it flows through the bearing, which particles are then fed to a particle detection sensor by the further oil flow.

A first and a second electrical contact are arranged in the measurement area, with the two electrical contacts being arranged at a distance from one another. A gap between the two contacts is preferably formed by the distance, through which the contacts are electrically separated from one another. In particular, the two electrical contacts are connected to a power source, with the circuit being broken in the measurement area. The two electrical contacts can be arranged at a distance of less than 1 mm, preferably less than 0.5 mm, in particular less than 0.1 mm from one another. As an alternative or optionally in addition, individual particles larger than 0.1 mm, preferably more than 0.5 mm, in particular more than 1 mm, can be detected through the electrical contacts. Ultimately, however, this is not the case pure particle size is decisive for a successful detection, but much more the volume formed by the particles, which specifies an electrical resistance and enables a current conduction between the contacts in the first place.

The procedure is characterized by the following steps:

- Generation of a magnetic field in the gear section, wherein the magnetic field is set up to move at least one ferromagnetic, in particular electrically conductive, particle arranged in the gear section towards the measuring area, so that a, in particular electrically conductive, bridge is formed from one or more of the ferromagnetic particles between the two electrical contacts forms or are formed;

- Generating a measured value based on an electrical parameter between the two electrical contacts;

- Determining a measure of the criticality of a flight operation based on the measured value.

The magnetic field can, for example, be generated permanently or temporarily, in particular for the duration of the measurement. The magnetic field is preferably generated within the gap. In particular, an effective area of the magnetic field, ie the area in which the ferromagnetic particles are attracted by the magnetic field, is arranged within the measuring area or overlapping the measuring area.

In particular, the bridge is only formed when one or more of the ferromagnetic particles are arranged in the measuring area. When the electrically conductive bridge is formed, the distance or gap between the two electrical contacts is preferably bridged, so that the electric circuit is closed and the measured value is generated. In particular, depending on the particle size, the bridge can be formed by exactly one ferromagnetic particle or by an agglomeration of several of the ferromagnetic particles in the measurement area or within the gap. The electrical parameter can in particular be an impedance. In particular, in an arrangement of at least one ferromagnetic Particles between the electrical contacts a change in impedance, it being possible to draw conclusions about a quantity and/or size of the ferromagnetic particles based on the change in impedance. The real part and/or the imaginary part of the impedance is preferably evaluated. It should be noted that the electrical parameter of capacitance, frequency, conductivity, or the like can be detected directly or indirectly.

In particular, the measured value can be evaluated using an evaluation criterion in order to determine the measure of the criticality. For example, the evaluation criterion can be defined by a stored target value or value range with which the recorded measured value is compared. For example, the measured value can be converted into a comparable value as part of the evaluation. Alternatively, however, the measured value can also be evaluated directly. In particular, based on the degree of criticality, a decision can be made as to whether there is damage to the gearbox and thus a risk to flight operations.

The advantage of the invention lies in particular in the fact that, based on the degree of criticality, the pilot is given the opportunity to make the decision to abort a mission independently during a mission. In addition, based on the measure of criticality, a qualitative statement on the condition of the gearbox can be made. The method can also be used to detect ferromagnetic particles in the transmission in a simple and cost-effective manner, with the number and size of the detected particles being able to be inferred at the same time by evaluating the electrical parameter.

In a specific implementation, it is provided that a warning signal is generated based on the measure of the criticality, with a measure of the criticality of the flight operation being displayed based on the warning signal. The warning signal is preferably output in real time when a current measured value meets the evaluation criterion. The warning signal can be output as an electrical signal, for example, which is provided for further processing by a computing and/or display device. In particular, the measure of the criticality can be displayed visually and/or acoustically and/or haptically. It can thus in a simple way the pilot is informed that there is a threat to flight operations, where the pilot can make a decision regarding the mission based on the display.

A preferred development provides that the measure for the criticality is divided into at least or exactly two criticality levels, with a corresponding warning signal being generated for each of the criticality levels. Information regarding the criticality can preferably be transmitted via the warning signal. In particular, at least one associated evaluation criterion can be defined for each criticality level, which must be fulfilled so that the criticality is displayed accordingly. The criticality levels are preferably classified on the basis of the particle size and/or number of particles, which can be determined on the basis of the electrical characteristic or a change in the electrical characteristic. The gradual display of the criticality can show the pilot in a simple way whether the mission has to be aborted or the mission can be ended, if necessary with restrictions.

In a further specification, it is provided that no criticality is displayed in a first criticality level, low criticality is displayed in a second criticality level and high criticality is displayed in a third criticality level. For example, the first level is displayed if no particles or only a small number of particles with a small particle size, e.g. less than 10 microns, are detected. For example, the second stage is indicated when one or a few particles with a mean particle size, e.g., greater than 10 microns and/or less than 50 microns, are detected. For example, the third stage is indicated when at least one particle with a large particle size, e.g., greater than 50 microns, and/or a high number of particles are detected. Due to the different levels of criticality, damage to the gearbox can be reliably classified so that the pilot can better assess the risk of flight operations.

In a further implementation, it is provided that the measure of the criticality of flight operations is evaluated based on at least one further measured value, which is recorded independently of the measured value. In particular, the at least one further measured value is recorded at the same time or simultaneously as the measured value and correlated with the measured value, with the criticality being evaluated as a function of the correlated measurement result. The measured value is preferably evaluated using at least one evaluation criterion. By taking into account at least one further measured value, the measurement reliability can be increased and, at the same time, a misinterpretation of an individual measured value can be reduced.

In a specification, it is provided that a low level of criticality is displayed if the measured value and/or the further measured value are divided into the second criticality level. In particular, a separate evaluation criterion is stored for each measured value, on the basis of which the measured value is divided into the respective criticality level. The measured values are preferably evaluated and/or evaluated based on a decision logic. Provision can optionally be made for the measured values to be weighted differently. For example, the weighting can be selected depending on a current operating state and/or the measuring point and/or the detected particles. For example, when particles are detected at typically neuralgic points, a high level of criticality can be indicated even if the further measured value does not meet the associated evaluation criterion or is divided into the first or second criticality level. Furthermore, a high level of criticality is indicated if the measured value and/or the further measured value are divided into the third criticality level. In particular, a high criticality is indicated if at least two or all measured values are classified in the third criticality level. Optionally, different weightings can also be taken into account. A method is thus proposed which compares and evaluates different measured values with one another, so that the measurement reliability is significantly increased.

In a further specification, it is provided that the further measured value is output when at least one further ferromagnetic particle is detected in a further measuring range in the transmission. In particular, the further measuring range can be arranged in the gear section or in a further gear section. Ferromagnetic particles are preferably detected in a further measuring range, as has already been described above. Especially ferromagnetic particles can be detected at at least or exactly two, preferably more than three, in particular more than five different positions or measurement areas in the transmission. Alternatively or optionally in addition, the further measured value is output when a transmission parameter changes. For example, one or more known transmission parameters such as vibrations, noise, speed, torque, transmission temperature or the like can be evaluated for this purpose. A method is thus proposed which is distinguished by a high level of measuring accuracy, with a failure of the transmission being able to be detected early and reliably by taking into account several measured values.

Provision is preferably made for the electrical parameter to be an ohmic resistance. In particular, particles with a small cross section have a higher resistance than particles with a larger cross section. For example, the ohmic resistance can be determined based on Ohm's law and provided as a measured value. The particle size can thus be determined on the basis of the ohmic resistance. Alternatively or optionally in addition, the electrical parameter is an electrical voltage. In particular, a voltage drops across the electrically conductive bridge, so that the voltage difference can be used to form the measured value. For example, the electrical voltage can be determined based on Ohm's law. The particle size can thus be determined on the basis of the voltage or a change in the voltage.

A further object of the invention is a monitoring system which is designed and/or suitable for monitoring a transmission in an aircraft. In particular, the monitoring system is designed and/or suitable for carrying out the method as already described above.

The monitoring system has at least or precisely one particle detection sensor, which is designed to detect ferromagnetic particles in a measuring area of the transmission. In particular, the particle detection sensor arranged in the transmission section of the transmission, wherein the particle detection sensor defines the measuring range. The measuring range is to be understood as an area around the sensor within which the ferromagnetic particles are detected. For this purpose, the particle detection sensor has two electrical contacts spaced apart from one another, which are arranged within the measuring area and are connected to an electrical circuit. The particle detection sensor is preferably designed as a chip detection sensor which is designed and/or suitable for detecting ferromagnetic and in particular metallic chips. Such sensors are also known as magnetic rubbing detectors (Magnetic Chip Detectors).

The particle detection sensor has a magnet which is designed and/or suitable for generating a magnetic field. The magnet can be designed as a permanent magnet or as an electromagnet. The magnet has the function of moving one or more ferromagnetic particles arranged in the gear compartment into the measuring range of the particle detection sensor, so that an electrically conductive bridge of one or more of the ferromagnetic particles is formed between the two electrical contacts. The magnet is preferably arranged in such a way that an effective area of the magnet, in which the ferromagnetic particles are magnetically attracted, is arranged between the two contacts and/or in the measuring area. For example, the magnet can be arranged between the two contacts in the gap for this purpose. If one or more of the ferromagnetic particles are present between the electrical contacts, they can be detected on the basis of the electrical parameter between the two contacts. The particle detection sensor is designed to output a measured value based on a measured electrical parameter. In particular, the measured value can be output as an electrical measurement signal.

The monitoring system also has an evaluation device which is designed and/or suitable for evaluating the measured value in order to determine a measure of the criticality of flight operations by evaluating the measured value. The particle detection sensor and the evaluation device are preferably connected to one another in terms of signals. In particular, in the evaluation device at least one evaluation criterion is stored, based on which the measured value is mapped into the measure of criticality. For example, the evaluation device can be designed as a hardware or software module in a flight computer. The evaluation device is formed.

In a further embodiment it is provided that the monitoring system has at least or precisely one further particle detection sensor which is designed to detect ferromagnetic particles in a further measuring range of the transmission. In particular, the measuring area and the further measuring area are arranged at different positions of the transmission, in particular in different and/or separate transmission sections. Alternatively, however, the two measurement areas can also be arranged adjacent to one another, in particular in a common transmission section. For this purpose, the further particle detection sensor is optionally arranged in the gear section or in the further gear section. In particular, the particle detection sensor and the further particle detection sensor are of identical design. For example, the monitoring system can have more than two, in particular more than four, in particular more than six, of the particle detection sensors. The further particle detection sensor is designed to output a further measured value when at least one further ferromagnetic particle is detected. All particle detection sensors are preferably connected to the evaluation device in terms of signals. The evaluation device is designed to evaluate a measure of the criticality of flight operations based on the measured value and the further measured value. In particular, the evaluation device is designed to evaluate the criticality using a decision-making logic.

In an alternative or optionally supplementary embodiment, it is provided that the monitoring system has at least or precisely one transmission monitoring sensor, which is designed and/or suitable for detecting a transmission parameter. In principle, the transmission monitoring sensor can be designed as a temperature, speed or torque sensor. However, the transmission monitoring sensor is preferably designed as an acceleration sensor, which is used to detect suitable for absorbing vibrations in the gearbox. The transmission monitoring sensor is designed to output the transmission parameter as a further measured value and to transmit it to the evaluation unit. For this purpose, the transmission monitoring sensor and the evaluation device are connected to one another in terms of signals. The evaluation device is designed to evaluate a measure of the criticality of flight operations by evaluating the electrical measured value and the transmission parameter. In particular, the sensor data from a number of transmission monitoring sensors can be used and correlated with the measured values of the at least one particle detection sensor in order to assess the criticality.

A further embodiment provides that the monitoring system has a display device which is designed to display a measure of the criticality of flight operations. In particular, the display device is and/or can be arranged in the pilot's field of vision, preferably inside the cockpit. The display device is preferably designed as a light source or a display, which can assume at least two different display states to display the criticality. For example, the display states can be distinguished from one another by displaying different light signals and/or messages.

In a specific embodiment, it is provided that a v-shaped gap is formed between the two contacts, which gap is set up to accumulate several of the ferromagnetic particles. In particular, the two contacts are arranged at an angle of more than 20 degrees, preferably more than 50 degrees, in particular more than 80 degrees, to one another. Ferromagnetic particles of different sizes can be accumulated through the v-shaped gap. A measurement over time can be used to draw conclusions about normal abrasion or critical wear.

A further object of the invention relates to an aircraft with the monitoring system, as has already been described above. In principle, the aircraft can be in the form of an airplane, air taxi or the like. However, the aircraft is preferably designed as a helicopter. Further features, effects and advantages of the invention result from the following description of a preferred exemplary embodiment of the invention and the attached figures. show:

FIG. 1 shows a highly schematic representation of an aircraft with a monitoring system as an embodiment of the invention;

FIG. 2 shows a schematic representation of a particle detection sensor of the monitoring system according to FIG. 1;

FIG. 3 shows the particle detection sensor in the same representation as in FIG. 2 in a first detection state;

FIG. 4 shows the particle detection sensor in the same representation as in FIG. 2 in a second detection state;

FIG. 5 shows the particle detection sensor in the same representation as in FIG. 2 in a third detection state;

FIG. 6 shows a decision logic for evaluating a criticality of the flight operations using a schematic block diagram.

FIG. 1 shows an aircraft 1 in a highly schematic block diagram, shown here only as a functional block, as an exemplary embodiment of the invention. For example, the aircraft 1 is designed as a helicopter.

The aircraft 1 has a transmission 2, which is used to translate a drive torque to. For example, the transmission 2 can translate the drive torque from an engine to an engine and/or to one or more rotors. The transmission 2 is preferably designed as a mechanical transmission, for example a gear transmission, which is exposed to high torques and speeds during flight operations.

The transmission 2 can be divided into several transmission sections 3, 4, which are designed as sections of a transmission interior of the transmission 2, for example. For example, the transmission sections 3, 4 can be spatially separated from one another, e.g. wet and dry room. Alternatively, however, the transmission sections 3 , 4 can also define a common interior space of the transmission 2 .

The aircraft 1 has a monitoring system 5 which is used to monitor the transmission 2 during flight operations. For this purpose, the monitoring system 5 has at least one particle detection sensor 6, which is used to detect ferromagnetic particles. These ferromagnetic particles can form, for example, as a result of abrasion or damage to the transmission components as a result of the high loads. The particle detection sensor 6 is arranged in the first gear section 3 in order to detect any ferromagnetic particles arranged therein. In this case, the particle detection sensor 6 outputs a measured value when one or more ferromagnetic particles are detected.

Optionally, the monitoring system 5 can have a further particle detection sensor 7, which is arranged in the second gear section 4 for the detection of ferromagnetic particles. The additional particle detection sensor 7 can thus be used to detect ferromagnetic particles at different positions in the transmission 2 . In this case, the further particle detection sensor 7 outputs a further measured value when one or more ferromagnetic particles are detected.

Alternatively or optionally in addition, the monitoring system 5 can have a transmission monitoring sensor 8, which is used to record a transmission parameter. For example, the transmission monitoring sensor 8 as an acceleration tion sensor is formed, which is arranged to detect vibrations in or on the gear 2 Ge. The transmission monitoring sensor 8 outputs the transmission parameter as a further measured value.

The monitoring system 5 has an evaluation device 9 which is set up to evaluate the measured values. For this purpose, the sensors 6, 7, 8 are connected to the evaluation device 9 via signal technology. For example, the evaluation device 9 forms an integral part of a flight computer.

The evaluation device 9 has an evaluation module 10, the evaluation module 10 being designed to evaluate the measured values using at least one evaluation criterion in order to determine a measure of the criticality of flight operations. Furthermore, the evaluation device 9 can have an evaluation module 11 which is designed to correlate the measured values of the sensors 6, 7, 8 with one another and to evaluate the criticality on the basis of an evaluation criterion.

The evaluation device 10 is designed to output a warning signal if at least one evaluation criterion and/or evaluation criterion is met, the warning signal being provided to a display device 12 . The display device 12 can, for example, be in the form of a lamp, with the display device 13 converting the warning signal into a light signal in order to display the measure of the criticality of flight operations. For this purpose, the display device 10 is preferably arranged in the pilot's field of vision, with the pilot deciding on the basis of the light signal whether the mission must be aborted or whether the mission can be ended.

FIG. 2 shows, in a schematic representation, the particle detection sensor 6 as a further exemplary embodiment of the invention. It should be pointed out that the following description of the function can be applied analogously to the additional particle detection sensor 7 .

The particle detection sensor 6 has a first and a second electrical contact 13, 14, which are electrically separated from one another by a distance A are and within the respective transmission section 3, 4 are arranged. The two contacts 13, 14 are connected to an electrical circuit which in the area of the contacts 13, 14 through the gap formed between the contacts 13,

14 is interrupted.

The particle detection sensor 6 has a magnet 15 which generates a magnetic field F within the transmission section 3 . For example, the magnet

15 may be designed as a permanent magnet or as an electromagnet. The magnet 15 is preferably arranged between the two contacts 13, 14, so that a ferromagnetic particle arranged in the gear section 3 is moved into a measuring range M of the particle detection sensor 6 due to the magnetic interaction. The measuring area 5 is to be understood as the area of the particle detection sensor 6 in which the ferromagnetic particles can make contact with the contacts 13, 14 or can accumulate on them.

FIGS. 3 to 5 each show the detection of different particle sizes or numbers by the particle detection sensor 6, as has already been described in FIG. In a detection state, at least one particle 17 is arranged between the two contacts 13, 14, the presence of one or more particles 17 being detectable between the two contacts 13, 14 based on an electrical parameter, in particular a change in impedance. Depending on the particle size and/or number, an electrically conductive bridge 16 is preferably formed from one or more particles 17, which bridges the two contacts 13, 14 so that the circuit is closed.

The measured value output by the particle detection sensor 6 is evaluated using an evaluation criterion stored in the evaluation module 10 in order to determine a measure of the criticality of the flight operation. In this case, the electrical parameter can be, for example, an ohmic resistance or a voltage, which is evaluated according to Ohm's law. The measure of the criticality is determined on the basis of the detected particle size and/or number. For example, a particle 17 with a small cross-section has a higher electrical Resistance than a particle 17 with a larger cross section, so that the electrical resistance can be used to draw conclusions about the particle size. In addition, depending on the time, conclusions can be drawn about how many particles 17 have accumulated on the particle detection sensor 6 within a specified period of time.

For example, the evaluation device 9 is designed to subdivide the measure of criticality into three levels, with no criticality being displayed in a first level, low criticality in a second level and high criticality in a third level by the display device 12 . The classification of the levels is based on the determined particle size or number. For example, the first stage is displayed when no particles 17 are detected by the particle detection sensor 6 . For example, the second stage is indicated when a single particle 17 having a maximum allowable particle size, e.g., less than or equal to 50 microns, is detected as shown in FIG. For example, the third stage is displayed when a particle 17 is detected that is larger than the maximum allowable particle size, as shown in Figure 4, and/or when multiple particles 17 are detected within the specified period of time at the particle detection sensor 6, such as shown in Figure 5. For example, the display device 12 can be designed to display the individual stages as different colors, e.g. traffic light colors. For example, the first level can be displayed as a green light, the second level as a yellow light, and the third level as a red light. This gives the pilot the opportunity to decide whether it is necessary to abort flight operations.

FIG. 6 uses a flow chart to show decision logic for evaluating the criticality during flight operations.

In a first method step V1, the measured value of the particle detection sensor 6 is made available to the evaluation device 9 and possibly converted into a value that can be evaluated. In a second method step V2, the measured value is evaluated and divided into one of the three criticality levels S1, S2, S3.

In order to avoid misinterpretation of the measured value, the measured value of the additional particle detection sensor 7 and/or the transmission monitoring sensor 8 is added in a third method step V3 and divided into one of the three criticality levels S1, S2, S3 if the measured value of the particle detection sensor 6 is in the second Method step V2 is divided into the second or third criticality level S2, S3.

In a fourth method step V4, based on the respective criticality level

51, S2, S3 generates a warning signal and makes it available to the display device 12, the display device 12 being designed to display the respective criticality level S1,

52, S3 based on the warning signal. The display device 12 displays the first stage S1 until a particle 17 is detected by the particle detection sensor 6 .

If the measured value of the particle detection sensor 6 is divided into the second or third criticality level S2, S3 as part of the second method step V2 and the measured value of the further particle detection sensor 7 and/or the transmission monitoring sensor 8 is divided into the third criticality level S3 as part of the third method step V3 generates a warning signal to display the third criticality level S3 as part of the fourth method step V4.

If, on the other hand, the measured value of the particle detection sensor 6 is divided into the second or third level S2, S3 as part of the second method step V2 and the measured value of the further particle detection sensor 7 and/or the transmission monitoring sensor 8 is divided into the second criticality level S3 as part of the third method step V3, a warning signal for displaying the second criticality level S2 is generated as part of the fourth method step V4. The pilot thus receives a qualitative statement on the state of the gearbox 2, with the pilot being able to decide on the basis of the display whether he can end the flight or has to interrupt it. reference sign

1 aircraft

2 gears

3 first gear section

4 second gear section

5 surveillance system

6 particle detection sensor

7 additional particle detection sensor

8 gearbox monitoring sensor

9 evaluation device

10 evaluation module

11 Rating Module

12 display device

13 first contact

14 second contact

15 magnets

16 conductive bridge

17 ferromagnetic particles

A distance

F magnetic field

M measuring range

V1-V4 process steps S1-S3 criticality levels

Claims

patent claims

1. A method for monitoring a transmission (2) in an aircraft (1), wherein the transmission (2) has at least one transmission section (2) with at least one measuring range (M), wherein in the measuring range (M1) a first and a second electrical contact (13, 16) are arranged at a distance (A) from one another, at which:

- a magnetic field (F) is generated in the gear section (2), the magnetic field (F) being set up to move at least one ferromagnetic particle (17) arranged in the gear section (2) towards the measuring area (M1), so that a bridge (16) of one or more of the ferromagnetic particles (17) forms between the two electrical contacts (13, 14);

- Based on an electrical parameter between the two electrical contacts (13, 16), a measured value is generated;

- based on the measured value, a measure of the criticality of flight operations is determined.

2. The method as claimed in claim 1, characterized in that a warning signal is generated based on the measure of the criticality, a measure of the criticality of the flight operation being displayed based on the warning signal.

3. The method as claimed in claim 2, characterized in that the measure of criticality is divided into at least two criticality levels (S1, S2, S3), a corresponding warning signal being generated for each of the criticality levels (S1, S2, S3).

4. The method according to claim 3, characterized in that no criticality is displayed in a first criticality level (S1), low criticality is displayed in a second criticality level (S2) and high criticality is displayed in a third criticality level (S3). .

5. The method as claimed in one of the preceding claims, characterized in that the measure of the criticality is evaluated based on at least one further measured value which is recorded independently of the measured value.

6. The method according to claim 5, characterized in that a low criticality is displayed when the measured value and/or the further measured value are divided into the second criticality level (S2), and that a high criticality is displayed when both the measured value and/or the further measured value can be divided into the third criticality level (S3).

7. The method according to claim 5 or 6, characterized in that the further measured value is output when at least one further ferromagnetic particle (17) is detected in a further measuring range (M2) of the transmission (2) and/or when a change occurs Transmission parameter of the transmission (2) is generated.

8. The method according to any one of the preceding claims, characterized in that the electrical parameter is an ohmic resistance and / or a voltage.

9. Monitoring system (5) for a gearbox (2) in an aircraft (1), with at least one particle detection sensor (6) for detecting ferromagnetic particles (17) in a measuring range (M1),

- wherein the particle detection sensor (6) is arranged in a gear section (3) of the gear bes (2),

- wherein the particle detection sensor (6) has two spaced apart electrical contacts (13, 14),

- Wherein the particle detection sensor (6) has a magnet (15) for generating a magnetic field (F), the magnet (15) being designed to move a ferromagnetic particle arranged in the gear section (3) into a measuring range (M1) of the particle detection sensor ( 6) to move so that an electrically conductive bridge (16) is formed from one or more of the ferromagnetic particles (17) between the two electrical contacts (13, 14),

- wherein the particle detection sensor (6) is designed to output a measured value based on an electrical parameter between the two electrical contacts (16, 17), with an evaluation device (9) for evaluating the measured value,

- The evaluation device (9) being designed to determine a measure of the criticality of flight operations by evaluating the measured value.

10. Monitoring system (5) according to Claim 9, characterized by at least one further particle detection sensor (7) for detecting ferromagnetic particles (17) in a further measuring range (M2) of the transmission (2), the further particle detection sensor (7) in the gear section (3) or a further gear section (4), the further particle detection sensor (7) being designed to output a further measured value when at least one further ferromagnetic particle (17) is detected, the evaluation device (9) being formed, to evaluate a measure of the criticality of flight operations based on the measured value and the further measured value.

11. Monitoring system (5) according to claim 9 or 10, characterized by at least one transmission monitoring sensor (8) for detecting a transmission parameter of the transmission (2), the evaluation device being designed, the transmission monitoring sensor (8) being designed to detect the transmission parameter output as a further measured value, the evaluation device (9) being designed to evaluate a measure of the criticality of the flight operation based on the measured value and the transmission parameter.

12. Monitoring system (5) according to one of claims 9 to 11, characterized by a display device (12), wherein the display device (12) is designed to display the criticality of flight operations.

13. Monitoring system (5) according to any one of claims 9 to 12, characterized in that between the two contacts (13, 14) a V-shaped gap is formed, which is set up to fen several of the ferromagnetic particles to pile up.

14. Aircraft (1), characterized by a monitoring system (5) according to one of Claims 9 to 13.